Instantaneous Phase-Shifting Lateral-Shearing Interferometer

A simple instantaneous phase-shifting lateral-shearing interferometer is described. This interferometer uses only one wedge plate and two identical transmission gratings. The two identical gratings generate equally spaced identical multiple test beams, which are necessary for instantaneous phase-shifting interferometry. The multiple test beams generated by the two gratings are incident on the wedge plate along the wedge direction. The optical path difference between the original wavefront and the sheared wavefront depends on the incident position of the test beam on the wedge plate because the wedge thickness varies along the wedge direction. This optical path difference gives a phase shift corresponding to each interferogram. A. numerical expression is derived and an experimental result is shown.